1. Technical Field
The technology disclosed herein relates to a noise reduction device used in a seat in a sealed structure such as an aircraft or a railway car.
2. Background Information
When an internal space is utilized in which the boundaries are formed by continuous walls, such as in an aircraft or a vehicle, the utilized space becomes a kind of sealed structure, and if there is a noise source inside or outside the utilized space, the users of the space are stuck in a noisy environment.
Particularly with an aircraft, the main noise sources are noise from the machinery that generates the aircraft's thrust, such as propellers or engines, and wind noise as the aircraft nose and wings slice through the air during flight. Therefore, noise inside the cabin can be uncomfortable for the passengers, and also makes it harder to hear announcements and so forth, so there is a great need for improvement in this area.
In view of this, a method in which a noise reduction device is installed at each seat has been proposed to improve passenger comfort (see WO2009/078147 and Japanese Laid-Open Patent Application H7-160275, for example). This noise reduction device comprises a microphone that detects noise generated from a noise source, a controller that inverts the phase of and amplifies the output signal of the microphone, and a speaker that converts the output signal of the controller into sound.